Method for remote detection of gaseous substances in the atmosphere by the DIAL system with two lasers and a remote detector

Abstract

A system and method for remote detection of gaseous substances by a DIAL system includes causing a laser beam generated by a first laser to impinge on a semipermeable mirror, wherein 50% of the laser beam power passes through the semipermeable mirror and proceeds through a first aperture towards a target, wherein a remaining 50% of the laser beam power reflects from the semipermeable mirror and impinges on a reflecting mirror from which it is reflected. The method may also include causing a delayed laser beam generated by a second laser to impinge on the semipermeable mirror, wherein 50% of the laser beam power passes through the semipermeable mirror and impinges on the reflecting mirror from which it is reflected and is directed through the second aperture to the target and at the same time a remaining 50% of the laser beam power reflects from the semipermeable mirror.

1 . A device comprising:
 a first laser associated with a differential absorption LIDAR (DIAL) system;   a second laser associated with the DIAL system;   a semipermeable mirror associated with the DIAL system disposed at least partially at a convergence of axes of a first laser beam from the first laser and a second laser beam from the second laser;   a reflecting mirror associated with the DIAL system disposed at least partially behind the semipermeable mirror and located in a forward direction of the second laser beam in a reflected direction from the semipermeable mirror of the first laser beam;   a first aperture associated with the DIAL system disposed in a forward direction from the semipermeable mirror such that a first portion of the first laser beam passes through the semipermeable mirror and impinges on the reflecting mirror and a second portion of the second laser beam is reflected; and   a second aperture associated with the DIAL system disposed in the reflected direction such that the first portion and the second portion are reflected, wherein the first aperture and the second aperture are configured to detect a gaseous substance.   
     
     
         2 . The device of  claim 1 , further comprising a receiver configured to receive the first portion and the second portion and to analyze spectral characteristics of the first portion and the second portion to identify the gaseous substance. 
     
     
         3 . The device of  claim 1 , wherein the first laser and the second laser are configured to operate at different wavelengths to enable differential absorption measurements of the gaseous substance. 
     
     
         4 . The device of  claim 1 , wherein the second laser is configured to generate a delayed laser beam relative to the first laser to optimize detection of the gaseous substance. 
     
     
         5 . The device of  claim 1 , wherein the device is configured to maintain gaseous substance detection capabilities when at least one of the first aperture or the second aperture is at least partially blocked. 
     
     
         6 . A method for remote detection of gaseous substances comprising:
 causing a laser beam to at least partially impinge on a semipermeable mirror, wherein:
 a first portion of the laser beam passes through the semipermeable mirror and proceeds through a first aperture towards a target, and 
 a second portion of the laser beam reflects from the semipermeable mirror and impinges on a reflecting mirror which redirects the second portion through a second aperture toward the target; 
   causing a delayed laser beam to impinge on the semipermeable mirror, wherein:
 a third portion of the delayed laser beam passes through the semipermeable mirror and impinges on the reflecting mirror which redirects the third portion through the second aperture to the target; and 
 a fourth portion of the delayed laser beam reflects from the semipermeable mirror and proceeds through the first aperture towards the target; and 
   detecting, based at least in part on causing the delayed laser beam to impinge on the semipermeable mirror, a gaseous substance.   
     
     
         7 . The method of  claim 6 , further comprising receiving a reflected portion of at least one of the laser beam or the delayed laser beam and analyzing a spectral characteristic of the reflected portion to identify the gaseous substance. 
     
     
         8 . The method of  claim 6 , wherein the laser beam is generated by a first laser operating at a first wavelength and the delayed laser beam is generated by a second laser operating at a second wavelength different than the first wavelength, wherein a difference between the first wavelength and the second wavelength enables differential absorption measurements of the gaseous substance. 
     
     
         9 . The method of  claim 6 , further comprising positioning a first laser configured to generate the laser beam and a second laser configured to generate the delayed laser beam with respect to each other such that an intersection of axes of the laser beam from the first laser and the delayed laser beam from the second laser includes the semipermeable mirror. 
     
     
         10 . The method of  claim 6 , further comprising directing the first portion, the second portion, the third portion, and the fourth portion in parallel paths toward the target to cause laser radiation to pass through substantially identical volumes of atmosphere. 
     
     
         11 . The method of  claim 6 , wherein the method maintains gaseous substance detection capabilities when at least one of the first aperture or the second aperture is at least partially blocked. 
     
     
         12 . The method of  claim 6 , further comprising reducing a first power density at the first aperture and a second power density at the second aperture by dividing the laser beam and the delayed laser beam into separate pulses to increase vision safety. 
     
     
         13 . One or more non-transitory computer-readable media storing instructions executable by one or more processors, wherein the instructions, when executed, cause the one or more processors to perform operations comprising:
 causing a laser beam to at least partially impinge on a semipermeable mirror, wherein:
 a first portion of the laser beam passes through the semipermeable mirror and proceeds through a first aperture towards a target, and 
 a second portion of the laser beam reflects from the semipermeable mirror and impinges on a reflecting mirror which redirects the second portion through a second aperture toward the target; 
   causing a delayed laser beam to impinge on the semipermeable mirror, wherein:
 a third portion of the delayed laser beam passes through the semipermeable mirror and impinges on the reflecting mirror which redirects the third portion through the second aperture to the target; and 
 a fourth portion of the delayed laser beam reflects from the semipermeable mirror and proceeds through the first aperture towards the target; and 
   detecting, based at least in part on causing the delayed laser beam to impinge on the semipermeable mirror, a gaseous substance.   
     
     
         14 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising:
 receiving a fifth portion of at least one of the laser beam or the delayed laser beam; and   analyzing a spectral characteristic of the fifth portion to identify the gaseous substance.   
     
     
         15 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising a first laser associated with the laser beam and a second laser associated with the delayed laser beam, the operations further comprising configuring the first laser to operate the laser beam at a first wavelength and the second laser to operate the delayed laser beam at a second wavelength different than the first wavelength, wherein a difference between the first wavelength and the second wavelength enables differential absorption measurements of the gaseous substance. 
     
     
         16 . The one or more non-transitory computer-readable media of  claim 13 , wherein a device associated with the one or more processors is configured to maintain gaseous substance detection capabilities when at least one of the first aperture or the second aperture is at least partially blocked. 
     
     
         17 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising reducing a first power density of the first aperture and second power density of the second aperture by dividing the laser beam and the delayed laser beam into separate pulses to increase vision safety. 
     
     
         18 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising directing the first portion and the second portion in a parallel path toward the target to cause laser radiation to pass through substantially identical volumes of atmosphere. 
     
     
         19 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising positioning a first laser configured to cause the laser beam and a second laser configured to cause the delayed laser beam relative to each other such that a first axis of the laser beam and a second axis of the delayed laser beam intersect at the semipermeable mirror. 
     
     
         20 . The one or more non-transitory computer-readable media of  claim 13 , the operations further comprising causing a division of the laser beam based at least in part on providing a power to the laser beam such that the first portion and the second portion are substantially similar, wherein causing the division is configured to minimize an external influence of atmospheric effects on detection of the gaseous substance.